Greg Pederson, Steve Gray, Lisa Graumlich,
Dan Fagre, and J.J. Shinker
Need for Snowpack Reconstructions
• Critical for western water resources
– 60-80% of annual water resources
– Regional & Global post-1980s decline
• Need to contextualize
– i.e. establish bounds of “natural variability”
• Spatially-specific, long-term reconstructions will allow for
more robust investigation of ocean-atmosphere forcings
• Driver of physical and biological processes
– Ecological change studies
– River flow reconstructions
– Parameterization of glacier mass balance reconstructions
Project Goals
500+ year spatial
reconstructions of April 1
SWE for key USGS HUCs
Predominately use existing
tree-ring chronologies
Investigate ocean
-atmosphere forcings of
changes in SWE
Make data freely available
Physiological Basis
Plant Functional Groups
Deep rooted species
require snowpack for soil
infiltration of H2O in regions
with high ET
Timing of growth response
Past work
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SHALLOW ROOTED
WOODY PLANTS
DEEPER ROOTED
WOODY PLANTS
Cook et al.
Meko
Woodhouse
Stahle
Fritz
Luckman & Watson
etc…
Breshears & Barnes 1999 – Landscape Eco.
Primary Data
Major River Headwaters
Colorado River Headwaters
Yellowstone / Missouri River
Headwaters
Columbia River Headwaters
Data:
USGS Hydrologic Units
NRCS Snow Course Records
ITRDB, personal, and
collaborators moisture
sensitive tree-ring
chronologies
Example: DATA Quality
Station Data
• 37 SNOTEL
• 148 Snow Course
• 26 Stream Gages
• 37 Met Stations
170101
170102
Visit us at our poster for a full
analysis & cont. discussion
Snowcourse April 1 SWE
n=52
•52 Snowcourse sites •Consistent variability
•1937-2007
•QA/QC step
SNOTEL & Snowcourse Records
Strong relationships with Snowcourse April 1 SWE suggest:
2.
1. April 1 SWE reflects peak SWE
SNOTEL records have temporal integrity
Peak SWE, Peak Discharge & PDO
Strong relationships hold between regional streamflow and
synoptic drivers of winter precipitation
Colorado Plateau April 1 SWE
20th Century April 1 SWE Anomalies
1977
Colorado Plateau Region
-Pederson, Gray, Fagre, Shinker, and Graumlich (in prep)
20th Century April 1 SWE Anomalies
1971
Colorado Plateau Region
-Pederson, Gray, Fagre, Shinker, and Graumlich (in prep)
20th Century April 1 SWE Anomalies
1944
Colorado Plateau Region
-Pederson, Gray, Fagre, Shinker, and Graumlich (in prep)
Methods: Screening & Calibration
• 50 km buffer
• Select and export
chronologies
• Screen for April 1 SWE
sensitive records
Correlations (t and t-1)
• Calibrate & Validate
-Pederson, Gray, Fagre, Shinker, and Graumlich (in prep)
Results: The Good, The Bad & The Ugly
Upper Colorado April 1 SWE
Reconstructions:
• Regression: R2=65.6% - 50.2%
• PCA Regression: R2=49.0%
• Partial Least Squares Reg: R2=50.9%
Validation:
• PRESS
• Leave-One-Out
Upper Colorado April 1 SWE
Reconstructions:
• 821 year April 1 SWE reconstruction
• Good agreement between models
• High Interannual Variability
• 1387-1462 – 75 years low snowpack
• Notable Intensity: 1230-1264 & 1556-1596 “Mega-drought”
• Most Intense: 1872-1892
• 1285-1386 – 101 years generally high snowpack
• Fewer intense wet departures
• How important is interannual variability?
20th century
peaks
Droughts similar to 1977
• 1977 drought – 11 similar droughts in the past 821 years
• Higher April 1 SWE events in past centuries
Preliminary Results
• High quality and quantity of tree-ring and snowpack data
– Thanks to contributors and ITRDB
• Robust calibration of many level 6 Watersheds
– 9 successful reconstructions -R2 between 40 and 65%
– 9 need improvement R2 40 %
• Successful 821 year April 1 SWE Reconstruction for
Upper Colorado River Basin
• Reconstructions capture 16th century “Mega-drought”
• Interesting 20th century perspectives
Project Prospectus
Headwaters of the Columbia River
Yellowstone (Missouri) & Snake
(Columbia) River Headwaters
In progress: generating SWE reconstructions
Project Prospectus
• Other pilot regions completed by fall 2008
• Complete analysis of:
– Existing chronologies needing to be resampled
– Target species or site characteristics
– HUCs needing more tree-ring chronologies
• Analysis of large-scale drivers of snowpack variability
• Web-serve the data
Thanks…
Funding Acknowledgements
U.S. Geological Survey
Global Change Program
Western Mountain Initiative
National Science Foundation
Geography and Regional Sciences